The Fractal Engine is the sixteenth building, added in the Feedback Loop update. Its initial price is 310 quadrillion cookies and produces 150 billion CpS by converting cookies into even more cookies.

Fractal engines are twice as efficient. "They practically bake themselves!"

522

Mandelbrown sugar

Own 5 fractal engines

15.5 quintillion

Fractal engines are twice as efficient. "A substance that displays useful properties such as fractal sweetness and instant contact lethality."

523

Fractoids

Own 25 fractal engines

155 quintillion

Fractal engines are twice as efficient. "Here's a frun fract : all in all, these were a terrible idea."

524

Nested universe theory

Own 50 fractal engines

15.5 sextillion

Fractal engines are twice as efficient. "Asserts that each subatomic particle is host to a whole new universe, and therefore, another limitless quantity of cookies. This somehow stacks with the theory of nanocosmics, because physics."

525

Menger sponge cake

Own 100 fractal engines

1.55 septillion

Fractal engines are twice as efficient. "Frighteningly absorbent thanks to its virtually infinite surface area. Keep it isolated in a dry chamber, never handle it with an open wound, and do not ever let it touch a body of water."

526

One particularly good-humored cow

Own 150 fractal engines

155 septillion

Fractal engines are twice as efficient. "This unassuming bovine was excruciatingly expensive and it may seem at first like you were ripped off. On closer inspection however, you notice that its earrings (it's wearing earrings) are actually fully functional copies of itself, each of which also wearing their own cow earrings, and so on, infinitely. It appears your dairy concerns will be taken care of for a while, although you'll have to put up with the cow's annoying snickering."

527

Chocolate ouroboros

Own 200 fractal engines

155 octillion

Fractal engines are twice as efficient. "Forever eating its own tail and digesting itself, in a metabolically dubious tale of delicious tragedy."

528

Nested

Own 250 fractal engines

155 nonillion

Fractal engines are twice as efficient. "Clever self-reference or shameful cross-promotion? This upgrade apparently has the gall to advertise a link to orteil.dashnet.org/nested, in a tooltip you can't even click."

529

Space-filling fibers

Own 300 fractal engines

155 decillion

Fractal engines are twice as efficient. "This special ingredient has the incredible ability to fill the local space perfectly, effectively eradicating hunger in those who consume it! Knowing that no hunger means no need for cookies, your marketers urge you to repurpose this product into next-level packing peanuts."

530

Endless book of prose

Own 350 fractal engines

155 undecillion

Fractal engines are twice as efficient. " "There once was a baker named [bakeryName]. One day, there was a knock at the door; [bakeryName] opened it and was suddenly face-to-face with a strange and menacing old grandma. The grandma opened her mouth and, in a strange little voice, started reciting this strange little tale :"^{[note 1]}

531

The set of all sets

Own 400 fractal engines

1.55 tredecillion

Fractal engines are twice as efficient. "The answer, of course, is a definite maybe."

532

This upgrade

Own 450 fractal engines

15 quattuordecillion

Fractal engines are twice as efficient. "This upgrade's flavor text likes to refer to itself, as well as to the fact that it likes to refer to itself. You should really buy this upgrade before it starts doing anything more obnoxious."

Grandmas are twice as efficient. Fractal engines gain +1% CpS per 14 grandmas. "A fractal grandma to make more grandmas to make more cookies."

521

Recursive mirrors

15 Prisms, 15 Fractal engines and "Synergies Vol. I" purchased

66.2 sextillion

Prisms gain +5% CpS per fractal engine. Fractal engines gain +0.1% CpS per prism. "Do you have any idea what happens when you point two of these at each other? Apparently, the universe doesn't either."

533

Mice clicking mice

75 Cursors, 75 Fractal engines and "Synergies Vol. II" purchased

62 octillion

Cursors gain +5% CpS per fractal engine. Fractal engines gain +0.1% CpS per cursor. "Absolutely blasphemous(e)!"

534

Fortune #016

Random fortune from news ticker

24.111 quattuordecillion

Fractal engines are 7% more efficient and 7% cheaper. "It's good to see yourself in others. Remember to see yourself in yourself, too."

↑Shown as infinitely scrolling text displaying 35 characters at a time that wraps around to the beginning once it reaches the end (" strange little tale : "There once "). [bakeryName] is the name of your bakery.